In order to product bioproducts through fermentation process using microorganism, various kinds of nutrient components required for growth of microorganism need to be added to medium. The medium is generally classified into synthetic medium containing only components which are clearly defined in chemistry such as inorganic salts, amino acids, vitamins, and the like, and complex medium containing all components required for the growth of microorganism such as peptone, corn steep liquor, yeast extract, and the like, even though some of the components are not defined yet.
However, in the synthetic medium, there is a problem in that microorganisms which are not capable of being grown even in the synthetic medium containing all nutrient components known so far are present in many numbers. In particular, the cost of amino acids and vitamins to be added to the synthetic medium are significantly expensive, there is limitation in using the expensive materials as a nutrient component of a medium in microorganism fermentation process mass-producing low-cost materials such as biofuels and bioproducts.
Accordingly, effort to develop a complex nutrient source not only containing all nutrient components required for growth of the microorganism and production of desired metabolite through microorganism fermentation but also being cheap in cost has been actively conducted all over the world. As the complex nutrient source, there are peptone, corn steep liquor, yeast extract, and the like, wherein some of them have been used in industrial processes producing various materials required for food industry, such as organic acids, amino acids, nucleic acids, and the like, through microorganism fermentation.
In the case of peptone, the nutrient components required for the growth of the microorganism and the production of the desired metabolite through microorganism fermentation are present in an excessive amount; however, the cost thereof is relatively expensive to produce biofuels and bioproducts through microorganism fermentation.
In addition, corn steep liquor (CSL) has an advantage in that the cost is cheap; however, sulfuric acid is used in processing and immersing processes of corn, such that the sulfuric acid as contained in the corn steep liquor. The sulfuric acid may inhibit the growth of the microorganism and the production of the desired metabolite through microorganism fermentation. In addition, as compared to the peptone or yeast extract, the corn steep liquor has relatively insufficient nutrient components which are capable being utilized by the microorganism, such that a relative large amount of corn steep liquor needs to be added as compared to an amount of the peptone or the yeast extract. In fact, in the case of using the medium containing the corn steep liquor as the nutrient component for the growth of the microorganism and the production of the desired metabolite through microorganism fermentation, it has reported that a rate of the growth of the microorganism and productivity of the desired metabolite are decreased (Amartey et al., Bullet. Chem. Technol., Macedonia, 19:65, 2000 Silveira et al., Appl. Microbiol. Biotechnol., 55:442, 2001).
Meanwhile, the yeast extract is generally made of Saccharomyces cerevisiae which is used in breweries and baking industry, and is useful for enhancing productivity of the desired metabolite as well as promoting the growth of the microorganism. However, the yeast extract is made by extracting the yeast itself, such that the preparation cost is high.
Accordingly, the present inventors studied a method for producing bioproducts at high efficiency and low cost, and as a result, found that in the case of using fermented wastes remaining after biofuels are produced using microorganism fermentation, a large amount of fermented wastes are capable of being recycled as they are, and the bioproducts also have high productivity. In addition, the present inventors found that after the biofuels are produced, microorganism in fermented products is hydrolyzed before separating the biofuels to be obtained, the nutrient components in the fermented wastes remaining after the biofuels are separated are more increased, such that the bioproducts have remarkably high productivity, thereby completing the present invention.